Repackage AppHost / SingleFileHost using input file as template

[Washi1337]

Problem Description

Currently, the implementation of AppHost / SingleFileHost bundles requires the official apphost.exe or singlefilehost.exe template file from the .NET SDK for packaging new bundles. This is problematic, as not every host has the full SDK installed. Editing existing apphost bundles would therefore not work on these hosts, even though the input binary is effectively the template itself with just a few minor modifications.

Proposal

Allow for using the input binary as the template for apphost repackaging in BundleManifest.WriteUsingTemplate.

Alternatives

This kind of is already possible, but the current implementation assumes the template binary does not contain any bundle. Using the original code will thus result in an output file that is double the size because of a duplicated apphost bundle.

Additional Context

No response